The present disclosure relates generally to the field of obstacle detection and alerting. The disclosure more specifically relates to alerting for early detection of incursion events to allow avoidance of hazardous encounters. The disclosure describes a system and algorithm for detecting vehicles, objects, and other conditions that are or may be a threat to safe vehicle movements on the airport surface and providing an appropriate alert such that the vehicle operator, controller, control system, or automation may take action to reduce the likelihood of a potential collision.
Incursion alerting systems, such as runway incursion alerting systems, are utilized to determine if an obstacle is in the path of an aircraft or other vehicle. Conventional runway incursion alerting systems are generally one of two types. The first type utilizes signals cooperatively provided from the obstacle on or approaching the runway; the second type utilizes radar, electro optic, or electromagnetic signals to actively sense the presence of an obstacle on or approaching the runway without the obstacles' active cooperation.
The first type requires equipment operating on the obstacles, or utilizes some form of ground-based infrastructure that senses, detects, and informs the aircraft flight crew or controllers. The aircraft that is to be protected relies on operating equipment that is not solely on the ownship aircraft. These systems are not stand-alone systems.
The second type requires neither ground infrastructure nor the obstacle to be equipped in a special way. These are stand-alone systems. Stand-alone systems treat the obstacle as a target. The obstacle is detected as being a source or reflector of electro optic, electromagnetic, or radio frequency energy. Radar, light detection and ranging (LIDAR) systems, forward looking infrared (FLIR) systems, and optical camera based systems are examples of sensor systems used as part of this stand-alone obstacle detection system type.
Conventionally, the first type of runway incursion alerting system relies upon cooperative signals, which may include, for example, traffic alert and collision avoidance system (TCAS), and Automatic Dependent Surveillance (ADS) systems that are broadcast (ADS-B) or re-broadcast (ADS-R).
TCAS systems are required for all airliners flying in the United States air space today. TCAS devices have been designated to interrogate transponders of other aircraft, sometimes referred to as intruder aircraft. The TCAS system evaluates the threat of mid-air collision with the other aircraft and coordinates an avoidance maneuver for the aircraft. TCAS systems have been developed to reduce the likelihood of a mid-air collision, but have not been developed to reduce the likelihood of a collision on the airport surface, as is the case for the runway incursion alerting system.
ADS-B and ADS-R systems are capable of providing position, velocity, status, and identifier information broadcast from aircraft or other surface vehicles at regular intervals using information obtained from ground-based and satellite-based positioning system signals (e.g., LORAN, DME, and GPS) and onboard systems. ADS-B systems may use transponders (including, for example, Mode S, Universal Access Transceiver (UAT), and VHF Data Link (VDL) mode 4) and provide transmissions at regular intervals. ADS-R systems are ground systems that receive ADS-B broadcasts on a first data link and re-transmit the information onto one or more other data links.
In an ADS-B system, a Mode S transponder may be disposed in a first aircraft that regularly emits a squitter message. The squitter message is a radio frequency (RF) signal that is periodically generated by the radio-based transponder and broadcast for reception by both ground and aircraft systems that want to monitor and track the emitting aircraft's state. In an ADS-B system there is no requirement for a reply to the ADS-B squitter message.
In one conventional runway obstacle detection system of the first-type, objects which may enter a runway, such as other aircraft, emergency vehicles, maintenance vehicles, runway tugs, baggage carts, etc., may carry transponders which provide location information. The location information can be generated from a navigation sensor, such as a Global Navigation Satellite System (GNSS) receiver (e.g., in an ADS-B type system). The transponders may transmit information that is received and processed by a centralized control system on the ground which determines whether the object is on or near the runway. The location information can be determined directly on the aircraft or be provided to the aircraft from the centralized control system.
Such a system requires that all objects which would potentially incur the runway space would be equipped with a transponder and all transponders remain functioning properly. In many situations, such as in underdeveloped regions, for example, in third world countries, or small airports and the like, sufficient infrastructure may not be available to support equipping each aircraft, ground vehicle, and baggage cart with a transponder and to have an appropriate central control system. Further, such systems cannot provide transponders to obstacles that cannot be tagged. For example, deer and other large animals may present a hazard if they wander onto a runway.
In another conventional runway obstacle detection system, land-based radar systems are used to detect runway obstacles. Land-based systems, including for example Airport Surface Detection Equipment (ASDE), require infrastructure at each airport and can be susceptible to similar difficulties associated with airborne-based obstacle detection systems. ASDE systems typically include ground primary radar, which typically operate in the 9 to 15 GHz range. Land-based systems may transmit the position and other information for traffic and obstacles using Traffic Information Services—Broadcast (TIS-B). A land-based positioning system is being considered to determine the location of aircraft on the airport surface which uses signal transmission times as detected by multiple ground receivers, as opposed to using radar or GNSS systems to the determine location of vehicles. Such a system is called a multilateration system and it uses ground-based equipment to receive signals (e.g., secondary surveillance radar (SSR) transmissions) that are transmitted by suitably equipped aircraft. NASA is developing a runway incursion prevention system (RIPS) based upon ADS-B equipped aircraft, an airport database, and a multilateration system.
Conventional incursion alerting systems of the first and second-type have disadvantages. For example, ADS-B-type runway incursion alerting systems cannot provide protection against vehicles or other obstacles that are not equipped with ADS-B transponders. If construction equipment does not include an ADS-B transponder, that equipment does not appear as an obstacle in an ADS-B system. Although aircraft-based weather radar systems and other sensors can detect obstacles that do not include transponders, weather radar systems and other sensors are typically not able to duplicate the positional accuracies, detection rates, and low false alarm rates associated with ADS-B-type systems. Further, weather radar systems and other sensors may not be able to detect obstacles that are shielded by other solid obstacles or obstacles that are susceptible to inaccurate detection by radar or other sensor techniques.
Therefore what is needed is a runway incursion alerting system and algorithm that processes the ownship, traffic, obstacle, and airport data to compute runway incursion alerts and advisories for the crew. Also needed is a system and algorithm that accounts for the characteristics and quality (e.g., accuracy and integrity) of the enabling technologies. Also needed is a system and algorithm capable of being extended to new airport layouts, taxiways operations, and that can handle most runway and taxiway incursion scenarios. There is also a need for a runway incursion alerting system that integrates sensor and data link information from multiple aircraft subsystems to increase the accuracy and integrity of runway incursion detection.